Many different types of delivery systems for delivering beneficial agents such as pharmaceuticals for the prevention, treatment, and diagnosis of disease are known in the art. One type of delivery system is the subcutaneous implant which contains a supply of a beneficial agent and is implanted beneath the skin of a patient to deliver the beneficial agent over time. Some of the different types of subcutaneous implants include osmotic drug delivery implants, dissolvable or erodable pellet type implants, and diffusional implants. Some examples of osmotic delivery implant systems are described in U.S. Pat. Nos. 4,111,202; 4,111,203; and 4,203,439.
The process of placing subcutaneous osmotic implants and other types of implants under the skin has previously been performed by use of a trocar system which is a two piece system including a cannula and an obturator. With this system, an incision is first made through the skin and the cannula and obturator are inserted together through the skin. The obturator is then withdrawn leaving the cannula in place as a guide for inserting the implant. The implant is inserted through the cannula while the obturator is used to push the implant to the end of the cannula. The obturator is then used to force the implant out of the cannula while the cannula is withdrawn to deposit the implant in the channel previously occupied by the cannula. The cannula and obturator are then withdrawn completely leaving the implant in place beneath the skin.
This trocar insertion process requires substantial expertise in coordinating the pressing of the obturator and the withdrawing of the cannula to deposit the implant in the channel. If these two processes are not properly coordinated, the implant may be forced into the tissue so that the implant has to make its own channel as it is inserted. Forcing the implant into the tissue causes additional trauma to the tissue and may cause the implant to become damaged by the force exerted by the obturator.
This method of insertion of an implant with a trocar is relatively time consuming and cumbersome. In addition, with this prior art insertion method the removal of the obturator for insertion of the implant through the cannula and the reinsertion of the obturator increase the possibility that sterility of the implant site will be compromised during this process.
An implanting apparatus for use in subcutaneously implanting multiple pellets in animals, disclosed in U.S. Pat. No. 4,105,030, provides a one-handed implanting system which reduces the risk of trauma to the tissue due to forcing the implant into the tissue and reduces contamination. The animal implant apparatus includes a handle, a needle containing the pellets to be implanted, and a rod positioned within the needle for pushing the pellets out of the needle. Once the needle containing the pellets has been inserted subcutaneously, a spring loaded trigger on the handle is activated which causes the needle to be automatically withdrawn by a spring leaving the implanted pellets in place. However, the handle configuration of this implanting device is designed for use in animals, such as cattle, and due to it's size and shape would be difficult to use for inserting implants subcutaneously in humans. Further, it is not possible to control the motion of the needle in this device because the needle will automatically retract upon activation of the trigger. The complex spring loaded propelling system and trigger of this implant apparatus increase the chances that the device will jam and fail to eject the pellets when required.
Accordingly, it would be desirable to provide a device for insertion of subcutaneous implants which would simplify the insertion process, allow one handed implant insertion, provide better control over the insertion process, and improve reliability by avoiding implanter jams.